/*
 * Copyright 2007 ZXing authors
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.google.zxing;

/**
 * The general exception class throw when something goes wrong during decoding of a barcode.
 * This includes, but is not limited to, failing checksums / error correction algorithms, being
 * unable to locate finder timing patterns, and so on.
 *
 * @author Sean Owen
 */
public abstract class ReaderException extends Exception {

	// TODO: Currently we throw up to 400 ReaderExceptions while scanning a single 240x240 image before
	// rejecting it. This involves a lot of overhead and memory allocation, and affects both performance
	// and latency on continuous scan clients. In the future, we should change all the decoders not to
	// throw exceptions for routine events, like not finding a barcode on a given row. Instead, we
	// should return error codes back to the callers, and simply delete this class. In the mean time, I
	// have altered this class to be as lightweight as possible, by ignoring the exception string, and
	// by disabling the generation of stack traces, which is especially time consuming. These are just
	// temporary measures, pending the big cleanup.

	//private static final ReaderException instance = new ReaderException();

	// EXCEPTION TRACKING SUPPORT
	// Identifies who is throwing exceptions and how often. To use:
	//
	// 1. Uncomment these lines and the code below which uses them.
	// 2. Uncomment the two corresponding lines in j2se/CommandLineRunner.decode()
	// 3. Change core to build as Java 1.5 temporarily
	//  private static int exceptionCount = 0;
	//  private static Map<String,Integer> throwers = new HashMap<String,Integer>(32);

	private static final long serialVersionUID = -8226324339516760162L;

	ReaderException() {
		// do nothing
	}

	//public static ReaderException getInstance() {
	//    Exception e = new Exception();
	//    // Take the stack frame before this one.
	//    StackTraceElement stack = e.getStackTrace()[1];
	//    String key = stack.getClassName() + "." + stack.getMethodName() + "(), line " +
	//        stack.getLineNumber();
	//    if (throwers.containsKey(key)) {
	//      Integer value = throwers.get(key);
	//      value++;
	//      throwers.put(key, value);
	//    } else {
	//      throwers.put(key, 1);
	//    }
	//    exceptionCount++;

	//return instance;
	//}

	//  public static int getExceptionCountAndReset() {
	//    int temp = exceptionCount;
	//    exceptionCount = 0;
	//    return temp;
	//  }
	//
	//  public static String getThrowersAndReset() {
	//    StringBuilder builder = new StringBuilder(1024);
	//    Object[] keys = throwers.keySet().toArray();
	//    for (int x = 0; x < keys.length; x++) {
	//      String key = (String) keys[x];
	//      Integer value = throwers.get(key);
	//      builder.append(key);
	//      builder.append(": ");
	//      builder.append(value);
	//      builder.append("\n");
	//    }
	//    throwers.clear();
	//    return builder.toString();
	//  }

	// Prevent stack traces from being taken
	// srowen says: huh, my IDE is saying this is not an override. native methods can't be overridden?
	// This, at least, does not hurt. Because we use a singleton pattern here, it doesn't matter anyhow.
	public final Throwable fillInStackTrace() {
		return null;
	}

}
